Abstract:

In recent years, the production of methanol by CO₂ hydrogenation with green hydrogen produced from renewable energy sources has received a lot of attention. However, the CO₂ conversion and methanol selectivity of the reaction are limited by the thermodynamic equilibrium of CO₂ catalytic hydrogenation reaction. Moreover, the presence of water as a byproduct usually leads to catalyst deactivation. In this study, a mother liquid seeding method was used to prepare defect-free single-channel NaA zeolite membrane. Then Cu-based catalysts were filled on the membrane to create a zeolite membrane-catalyst bifunctional reaction system that allowed for the simultaneous hydrogenation of CO₂ to produce methanol and the on-line selective removal of water. XRD, SEM, N₂ isothermal adsorption-desorption, and H₂-TPR were used to characterize the physical and chemical properties of the NaA zeolite membranes and the catalysts. The catalysts performance for CO₂ hydrogenation were evaluated by the membrane reactor. The results showed that the reaction system can significantly increase the CO₂ conversion and effectively drive the reaction equilibrium forward compared with the conventional fixed-bed reactor. The CO₂ conversion was increased from 3.34% to 28.78% and the methanol yield was promoted from 3.28% to 27.62% at 250℃ and 3MPa.

Key words: carbon dioxide, hydrogenation, methanol, Cu-based catalysts, membranes, reactor

摘要：

近年来，利用可再生能源产生的绿氢与CO₂反应制备甲醇备受关注。然而，由于CO₂催化加氢反应受热力学平衡限制，CO₂的转化率与甲醇选择性较低；另外，副产物水易导致催化剂失活。本研究采用母液晶种法在 α-Al₂O₃膜管外制备了无缺陷的单通道NaA分子筛外膜，通过在膜管外填充Cu基催化剂，构建了一种分子筛膜-催化剂反应分离双功能反应体系，以同时实现CO₂加氢生成甲醇和在线选择性除水。通过XRD、SEM、N₂等温吸附-脱附、H₂-TPR表征技术对NaA分子筛膜和催化剂进行理化性质表征，并在膜反应器上对催化剂的CO₂催化加氢性能进行评价。结果表明，与传统固定床反应器对比，本反应体系可有效拉动反应平衡，大幅提高CO₂转化率。在250℃、3MPa条件下，CO₂转化率由3.34%提高至28.78%，甲醇收率由3.28%提高至27.62%。

关键词: 二氧化碳, 加氢, 甲醇, Cu基催化剂, 膜, 反应器